Work the search positions out when they are read, not on each line written

A view's search positions were worked out again from every write, and
each of those walks the whole view. Content arrives a line at a time, so
rendering into a searched view costs a walk per line. Streaming 2000
lines takes 565ms, where the same render into an unsearched view takes
about 10ms.

Mark the positions stale on a write instead, and work them out where they
are read: when the view is drawn, when a key steps through the matches,
when the status is asked for. That is at most once a frame, and the same
2000 lines now take 8ms.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/gocui/search_test.go

@@ -34,3 +34,25 @@ func TestSearchStatusAfterTheMatchesChange(t *testing.T) {
 	assert.Equal(t, 0, index)
 	assert.Equal(t, 1, total)
 }
+
+func TestSearchPositionsFollowStreamedContent(t *testing.T) {
+	v := NewView("name", 0, 0, 40, 10, OutputNormal)
+	v.Search("match", nil)
+
+	// A render arrives a line at a time, and the status describes all of it.
+	writeLines(v, "other", "match", "other", "match")
+
+	_, total := v.GetSearchStatus()
+	assert.Equal(t, 2, total)
+}
+
+func BenchmarkWriteToSearchedView(b *testing.B) {
+	for b.Loop() {
+		v := NewView("name", 0, 0, 100, 40, OutputNormal)
+		v.Search("match", nil)
+		for i := range 2000 {
+			fmt.Fprintf(v, "line %d of a diff, most of which does not match\n", i)
+		}
+		v.GetSearchStatus()
+	}
+}

pkg/gocui/view.go

@@ -271,6 +271,12 @@ type searcher struct {
 	currentSearchIndex int
 	onSelectItem       func(*View, int)
 	renderSearchStatus func(*View, int, int)
+
+	// Whether the content has changed since the positions were worked out, so that
+	// they have to be worked out again before they are read. Working them out walks
+	// the whole view, and content arrives a line at a time, so it happens once per
+	// read rather than once per line written.
+	positionsStale bool
 }
 
 func (v *View) setRenderSearchStatus(renderSearchStatus func(*View, int, int)) {
@@ -287,7 +293,27 @@ func (v *View) renderSearchStatus(index int, itemCount int) {
 	}
 }
 
+// refreshSearchPositions works the search positions out again if the content has
+// changed since they were last worked out. Every read of the positions goes through
+// this, so that no caller has to know whether the view has been drawn since the
+// content it is asking about arrived.
+func (v *View) refreshSearchPositions() {
+	v.writeMutex.Lock()
+	defer v.writeMutex.Unlock()
+
+	v.refreshSearchPositionsIfNeeded()
+}
+
+// refreshSearchPositions for a caller that already holds writeMutex.
+func (v *View) refreshSearchPositionsIfNeeded() {
+	if v.searcher.positionsStale {
+		v.updateSearchPositions()
+	}
+}
+
 func (v *View) gotoNextMatch() error {
+	v.refreshSearchPositions()
+
 	if len(v.searcher.searchPositions) == 0 {
 		return nil
 	}
@@ -307,6 +333,8 @@ func (v *View) gotoNextMatch() error {
 }
 
 func (v *View) gotoPreviousMatch() error {
+	v.refreshSearchPositions()
+
 	if len(v.searcher.searchPositions) == 0 {
 		return nil
 	}
@@ -328,6 +356,8 @@ func (v *View) gotoPreviousMatch() error {
 }
 
 func (v *View) SelectSearchResult(index int) {
+	v.refreshSearchPositions()
+
 	itemCount := len(v.searcher.searchPositions)
 	if itemCount == 0 {
 		return
@@ -347,6 +377,8 @@ func (v *View) SelectSearchResult(index int) {
 
 // Returns <current match index>, <total matches>
 func (v *View) GetSearchStatus() (int, int) {
+	v.refreshSearchPositions()
+
 	return v.searcher.currentSearchIndex, len(v.searcher.searchPositions)
 }
 
@@ -420,6 +452,8 @@ func (v *View) nearestSearchPosition() int {
 }
 
 func (v *View) SetNearestSearchPosition() {
+	v.refreshSearchPositions()
+
 	if len(v.searcher.searchPositions) > 0 {
 		newPos := v.nearestSearchPosition()
 		if newPos != v.searcher.currentSearchIndex {
@@ -902,7 +936,7 @@ func (v *View) write(p []byte) {
 
 	v.buf.write(v, p)
 
-	v.updateSearchPositions()
+	v.searcher.positionsStale = true
 }
 
 // write parses p into cells and appends them to the buffer at its write cursor.
@@ -1353,6 +1387,8 @@ func stringToGraphemes(s string) []string {
 }
 
 func (v *View) updateSearchPositions() {
+	v.searcher.positionsStale = false
+
 	if v.searcher.searchString != "" {
 		var normalizeRune func(s string) string
 		var normalizedSearchStr string
@@ -1466,6 +1502,7 @@ func (v *View) draw(isWindowFocused bool) {
 	}
 
 	v.refreshViewLinesIfNeeded()
+	v.refreshSearchPositionsIfNeeded()
 
 	visibleViewLinesHeight := v.viewLineLengthIgnoringTrailingBlankLines()
 	if v.Autoscroll && visibleViewLinesHeight > maxY {
@@ -2075,6 +2112,8 @@ func (v *View) setContentLineCount(lineCount int) {
 // result that is visible in the view, if any, or the first one that is below the view if none is
 // visible.
 func (v *View) selectVisibleSearchResultAfterScrollUp() {
+	v.refreshSearchPositions()
+
 	if !v.Highlight && len(v.searcher.searchPositions) != 0 {
 		windowBottom := v.oy + v.InnerHeight()
 		if v.searcher.searchPositions[v.searcher.currentSearchIndex].Y >= windowBottom {
@@ -2098,6 +2137,8 @@ func (v *View) selectVisibleSearchResultAfterScrollUp() {
 // result that is visible in the view, if any, or the last one that is above the view if none is
 // visible.
 func (v *View) selectVisibleSearchResultAfterScrollDown() {
+	v.refreshSearchPositions()
+
 	if !v.Highlight && len(v.searcher.searchPositions) != 0 {
 		if v.searcher.searchPositions[v.searcher.currentSearchIndex].Y < v.oy {
 			newSearchIndex := v.searcher.currentSearchIndex